Yesterday it was a 14-year-old schoolboy stabbed in Lewisham, and three teenagers stabbed in north Kensington. On Saturday, a 19-year-old university student was shot dead in Clapton and a 16-year-old was stabbed to death in Wandsworth. The spate of killings and woundings in the past week has taken a grim toll on young lives. Gang violence, to which most of the attacks can be attributed, is a continuing scourge, a blight on the capital.